First generation digital terrestrial broadcasting standards include integrated services digital broadcasting-terrestrial (ISDB-T), digital video broadcasting-terrestrial (DVB-T), advanced television systems committee (ATSC), integrated services digital broadcasting-satellite (ISDB-S), digital video broadcasting-satellite (DVB-S), and the like which use a Reed Solomon (RS) code as an external code and a convolutional code as an internal code of an error correcting code.
In addition, practical use of second generation terrestrial digital broadcasting standards including digital video broadcasting-terrestrial 2 (DVB-T2), digital video broadcasting-cable 2 (DVB-C2), digital video broadcasting-satellite 2 (DVB-S2), and the like which use Bose Chaudhuri Hocquenghem (BCH) as an external code and low density parity check (LDPC) as an internal code of an error correcting code has begun.
In the related art, an error correcting unit of a receiving device compliant with a first generation terrestrial digital broadcasting standard is implemented by a pipeline connection of a Viterbi decoding unit, a convolutional de-interleaver, and an RS decoding unit. However, recently, stable reception of digital terrestrial broadcasting has been required even for moving objects. Therefore, a diversity receiving technique, an error correction technique, and the like have been studied to increase reception performance.
For example, in the ISDB-T standard, in order to increase reception performance, introducing a space diversity technique using a plurality of receiving antennas and a concept of iterative decoding to the error correcting unit has been devised (for example, refer to Non-Patent Document 1).
For example, in an error correction unit of a related receiving device, since a likelihood of a bit succeeded in RS decoding among likelihoods of respective bits to which Viterbi decoding is performed becomes a likelihood that is closest to an encoding bit, a difference of a branch metric of branches in a trellis corresponding to the bit is large. Therefore, a survival path can be selected more accurately and a positive decoding probability of Viterbi decoding is improved. Further, since the decoding result of Viterbi decoding having an improved positive decoding probability is de-interleaved and becomes a part of the RS code word input to the RS decoding unit, the positive decoding probability of RS decoding is improved. As a result, reception performance is improved. Then, such an effect further increases when Viterbi decoding and RS decoding are repeated.
Further, the applicant of the present application proposes a receiving device that can reduce a memory used in an error correction process by that the likelihood converting unit controls decoding of a likelihood to improve reliability of a decoding result by using decoding results which are not delayed among decoding results after the delay by the byte de-interleaver (for example, refer to Patent Document 1).